Topic: FI CB500F into 1977 CB750F?

[ryguy85]

Currently have a 1977 CB750F that I finished building into a cafe bike about 2 years ago, and the motor/trans has always been "ok". It's always had a ticking noise in the engine I could never isolate (that has been getting louder), trans slips out of gear more often as time goes on, other little things that make me question how many miles it has left. So I've been looking to do a motor swap using a donor bike, something with modern controls, fuel injection, and was brainstorming the CB500F that Honda put into production a few years ago.

Ideally would take my cafe bike down to a rolling chassis, keeping the suspension, bars, brakes, tank, seat, and using the CB500F bike for engine, trans, cooling, full wiring harness, controls, cluster.

What I'm looking to find out, is anyone aware if this has been done before, or if it's even possible without doing a major tear up of the frame?

Donor bike I've got my eye on.
https://detroit.craigslist.org/mcb/mcy/d/honda-cb-500f/6694516378.html

[flybox1]

You could do a REALLY good engine rebuild for less than the cost of that 500....and still have a CB750 to re-sell.
It be much easier/faster/cheaper than HOPING the 500 shoehorned-in, and worked as you hoped.

[ryguy85]

Cost isn't my concern, neither is resale value as I plan to keep this bike for life (Wife had the cafe seat custom made for me as a wedding gift, another reason I'll never sell it)

[Bankerdanny]

While the power is comparable, the modern 500F is still a twin vs a 4 and your 750 engine could easily be built to make much more power. Heck, if money isn't really an issue, get one of the billet 1000 cc blocks and make it into a liter bike.

If you just like the challenge of the 500F engine I imagine you can find a way, although I suspect major frame mods would be required since the 500F is a DOHC wet sump design and is likely taller. I would start by tracking down a 750 frame and figuring out how to make it fit on that first, then transferring the mods to your bike's frame.

[ryguy85]

I like the idea of an old bike with a modern fuel injection engine, a hybrid of classic looks/modern power plant if you will. Pulling the motor and taking it somewhere to have a proper rebuild is an option as well, just have to research for finding the right shop to do the work.

[ryguy85]

Also have been thinking about picking up a 1990's Nighthawk 750 to use as a donor bike, swapping everything over to the 77 chassis. Won't have the FI, but would at least be keeping with 750-4 if I went this route

Recall reading previously making the DOHC motor fit into a SOHC frame is quite problematic though?

https://detroit.craigslist.org/mcb/mcy/d/1991-honda-cb750-nighthawk/6692561291.html

[sixthwisconsin]

This is interesting, most guys do the opposite of what you are thinking. They keep the frame, engine from the old bike and add modern components like GXSR front ends, electronics etc. I'll be curious to see what you come up with.

[slikwilli420]

Put a 600 Bandit engine in one. Lots of guys doing slabbie conversions to Kaws, should fit our frame too. Personally, I would build the crap out of the SOHC Honda engine. These are simple machines, and any issue should be a simple fix, especially given your lack of concern for cost.

[ryguy85]

Cost is still a concern within reason, spent enough on the bike to get it where it is today and don't need to double that price tag. I'm still looking for a decent bike shop in the SE Michigan area that I would trust to do the work (was burned for a heavy price tag with not much work years ago when I was doing this bike build).

To do an engine and trans rebuild (engine has a ticking noise that's been getting louder, lacking in power at times, trans occasionally grinds into gear or will slip out of gear, or sometimes just does not want to get into 5th gear) what could I expect to pay to have someone do the rebuild? $1000? $2000?